Biodiesel Fuel Quality

Biodiesel Fuel Quality &

Technical Overview

National Biodiesel Board Technician Outreach Program

Quality, Quality, Quality B100 must meet D 6751 prior to blending to insure trouble-free

use of B20 and lower blends

BQ-9000 fuel quality program helps to promote high quality fuel from producers and marketers

B20 and lower blends are recommended since most of the research and successful use of the fuel has been with these blends See NBB Toolkit document “Use of Biodiesel Blends Up to B20” for

more information

Blends over B20 require special precautions and should only be used by knowledgeable and experienced users See NBB document “Guidance on Biodiesel Blends Above B20” for

more information: http://www.biodiesel.org/pdf_files/fuelfactsheets/Use_of_Biodiesel_Blends_above_%2020.pdf

Why care about biodiesel quality?

Off specification biodiesel can cause engine operability problems

Quality is critical to continue to grow the industry There is NO room for off-specification fuel Customers need to receive consistent

quality from lot to lot, batch to batch Must be on-spec for tax credit and to be

legal fuel

Summary Biodiesel production review Key elements in ASTM Specifications and Standard

Test Methods ASTM Specification D 6751 – 08, the specification

of B100 (biodiesel) fuel is described in detail. Key properties of B 100 are discussed in terms of

their tests and specifications. Alternative testing procedures Other issues affecting fuel quality

Review of the Production Process

Biodiesel is produced by a chemical reaction between methanol (or ethanol) and an oil or fat, in the presence of a catalyst.

Requires a strong basic catalyst (NaOH or KOH) The reaction is called “Transesterification”

Changing one ester (vegetable oil) into another ester (biodiesel)

Oil + Alcohol yields Biodiesel + Glycerol

Transesterification (the biodiesel reaction)

Fatty Acid Chain

Glycerol

Methanol (or Ethanol)

One triglyceride molecule is converted into three mono alkyl ester (biodiesel) molecules

Biodiesel

Triglyceride

Potential Impurities: in Biodiesel

Methanol – Degrades some plastics and elastomers, corrosive; Can lower flashpoint to unsafe levels (fire safety)

Unconverted/partly converted oils (bound glycerin) – Results in very poor cold flow properties, injector and in-cylinder deposits, potential engine failure

Free Glycerin – Results in injector deposits, clogged fuel filters, deposit at bottom of fuel storage tank

Catalyst (caustic, NaOH) – Excessive injector, fuel pump, piston, and ring wear, filter plugging, issues with lubricant

All are limited by ASTM D6751 specification

ASTM Specifications ASTM D 6751 – 08:Standard Specification for Biodiesel

Fuel (B 100) Blend Stock for Distillate Fuels

ASTM D 6751 has two grades S500 S15 (Almost all biodiesel is already S15)

B100 Blending Component Specification

Recent changes: Oxidation

stability added

Major steps forward for passage of biodiesel blend specifications

Critical for obtaining OEM approval

Critical for ensuring that biodiesel performs as advertised so market can grow

D6751-07b Requirements

McCormick, R.L, Westbrook, S.R. “Biodiesel and Biodiesel Blends” Standardization News, page 28, April 2007

Property Test Method Limits UnitsCalcium & Magnesium EN 14538 5 max ppm(ug/g)Alcohol control

either Flash Point D 93 130 min. Degrees C or GC methanol EN 14110 0.2 % Volume

Flash Point D 93 93min. Degrees CKin. Viscosity, 40C D 445 1.9 - 6.0 mm?/sec.Sulfated Ash D 874 0.02 max. % massSulfur S500 D 5453 0.05 max (500) % mass (ppm)

S15 D 5453 0.0015 max (15) % mass (ppm)Copper Corrosion D 130 No. 3 max.Cetane number D 613 47 min.Cloud Point D 2500 Report degrees CCarbon Residue D 4530 0.05 max. % massAcid Number D 664 0.50 max. mg KOH/gFree Glycerin D 6854 0.020 % massTotal Glycerin D 6854 0.240 % massPhosphorous content D 4951 0.001 max % massDistillation, T90 AET D 1160 360 max degrees CNa/K, combined EN 14538 5 max ppm(ug/g)Oxidation Stability EN 14112 3 min hours

(Visual Appearance)D 4176 Free of un-dissolved water, sediment and suspended matterBOLD = BQ-9000 Critical Specification TestingOnce Production Process Under Control

ASTM Current Status ASTM D6751 is the approved standard for B100 to

be used for blending up to B20 in the US Several changes made to support blend specifications

B5 initially approved into the petrodiesel specifications: D975, D396 No changes to D975, D396 B100 must meet D6751 prior to blending

B6 to B20 for on/off road diesel engines approved draft as a stand alone specification Widest of #1/#2 specifications, T-90 5ºC increase Addition of stability and acid number for final blend B100 must meet D6751 prior to blending

B6-B20 Blend Specification

Oxidation Stability is 6 hours

Cold Soak Filtration Test included

Acid Number Reduction

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

•Under guidance of B20 Fleet Evaluation Team (OEM’s, NREL, NBB)

•Samples obtained nationwide from biodiesel blenders (27 samples)

•85% of samples tested met the ASTM D6751 specification

2004 B100 Quality Survey

Four samples failed with high levels of:

•phosphorus (lube oil contamination?)

•total glycerin•acid number•acid number and total glycerin

2006 B100 Quality Survey

A subcontractor visited the site of a biodiesel blender, usually a terminal operator or jobber, to collect the B100 sample

32 B100s, 6 B99s, and 1 B50

59% of B100 samples tested fail the D6751 specification Importantly, 30% fail total glycerin – immediate operational

problems in cold weather Other issue of concern is 20% failure rate for Na+K Compares to 15% failure rate in 2004 survey Samples were collected randomly, not on production volume basis

• Biodiesel, based on production volume, may have different failure rate

• Poor quality batch may have contaminated larger fuel lot

2007 B100 Quality Survey

Collect B100 samples directly from producers and analyze for properties most likely to impact engine performance and emission control systems Flash point, oxidation stability, acid value,

free and total glycerin, cloud point, Na+K, Ca+Mg, P, water & sediment

First survey that will link test results to production volume

Results presented at recent NBB meeting

Survey results 56 out of 107 producers participated in 2007

survey or 70% of the 2007 US market –Reasons for not participating are likely due to lack of feedstock availability

Wide variety of feedstocks represented Meeting the specification is independent of

producer size or feedstock Small producers failed specifications more

often than medium or large producers –Small producers: 28% of samples passed –

Medium producers: 68% of samples passed –Large producers: 94% of samples passed

How do you ensure quality?

Biodiesel Fuel Quality is determined by: 1. Feedstock quality 2. Production process 3. Post-Reaction monitoring 4. Analytical Capability5. Handling and Storage **CRITICAL

Critical ParametersFlashpoint, °CAcid Number, mg KOH/gTotal and Free Glycerin, % massWater and Sediment, volume %Cloud point, °COxidative Stability, hr Sulfur, ppmVisual appearance

Flash PointMethod ASTM D 93 Changed 2007- Limit: 93ºC minimum Temperature A sample is heated in a close vessel and ignited.

When the sample burns, the temperature is recorded.

Alcohol Control One of the following must be met: 1. Methanol content EN 14110: 0.2 max % volume 2. Flash point D 93 : 130 min °C

Flash Point Testing

Water and Sediment Method D 2709 Limit of 500ppm,

examining the free water content

100 mL of sample are centrifuged at 800 rcf for 10 min at 21° to 32°C in calibrated tube.

Water and Sediment

Biodiesel can absorb 1500 ppm of water while diesel only 50 ppm.

Free water can cause corrosion of fuel injection parts.

Housekeeping issue Precipitates above

cloud point

Karl Fischer : Moisture Determination

Acid Number Test Method ASTM D

664 Limits: 0.5 mg KOH/g

maximum pH sensitive electrode May also be

determined using indicators

Sulfated Ash Test Method ASTM D 874 Limits: 0.020 % mass maximum Sample ignited and burned Ash + carbon (C removed by

H2SO4) Indication of concentration of

metal additives (Ba, Ca, Mg, Na, K, Sn, Zn)

More than 0.020 % indicates residual soap & catalyst

Free and Total Glycerin Test Method ASTM D 6584 Limits: 0.020 % mass free glycerin 0.240 % mass total glycerin Gas Chromatography with FID

detection Quantifies glycerol, mono-, di- and

triglycerides

Production Factors: Total Glycerol

Measured with gas chromatograph (ASTM D6584) and requires a skilled operator.

Saturated monoglycerides have very low solubility in biodiesel.

If too high, there may be problems with fuel filter plugging and fuel stability.

Good conversion

Sulfur Test Method ASTM D 5453 Limits: 0.05 % mass maximum S oxidized to SO2 at high

temperatures UV fluorescence of emitted gases SO2

SO2* SO2

S limits dictated by environmental considerations (S15 or S500)

EPA regulations Feedstock variation

Cloud point Test Method ASTM D 2500 Limits: No established limits Reported in ºC Sample cooled and examined visually until first

cloud appears. Indicates the lowest temperature at which fuel is

usable. Generally higher than diesel.

Cold Flow Wax molecules in diesel fuel and biodiesel tend to

crystallize at low temperatures. Crystals agglomerate to form large masses. This can cause filter plugging and eventually the fuel will

become a solid mass. Soy biodiesel gels at approximately 32°F #2 petroleum diesel fuel gels at 10 to 14 °F. Biodiesel from saturated/tallow feedstocks can gel as

high as 50-55°F. In contrast, petroleum diesel fuel is a mixture of

hundreds of different compounds that solidify at very different temperatures. So, even if some compounds crystallize at a relatively high temperature, many other compounds will stay liquid to a much lower temperature.

Watch your soap & water content!

Cloud Point & CFPP

Cold Soak Filtration Test

Developed in response to questions about precipitates above the cloud point

Character of precipitates may vary with feedstock

Method is being incorporated in the D6751 on October 15, 2008

Method will be mandatory annex in D6751 until test method is balloted and written

ASTM Subcommittee 14 is working to further develop test method

-6°C

-10°C -12°C

-8°C

Cold Soak Filtration Test Method

Preheat fuel at 40°C for 3 hours to remove thermal memory then hold at room temp for 24 hours

Soak 300 mL sample at 4°C for 16 hours and let return to room temperature Time will vary with degree of

saturation of feedstock Filter fuel using 0.7m filter and

constant vacuum Record time to filter fuel

If fuel does not filter, record time stopped and volume filtered

Oxidative Stability Equipment: Rancimat or OSI Method: EN 14112; 3 minimum hours Equipment cost: 10k- 17k Recent addition to ASTM 6751 Products of oxidation in biodiesel are various acids or

polymers, can cause fuel system deposits and lead to filter plugging & fuel system malfunctions.

Additives can improve the oxidation stability performance of biodiesel.

Fuel oxidation Biodiesel will react with oxygen from the air

to form polymers, acids, etc. Acids:

Presence indicated by increasing Acid Value Cause corrosion of metal components Corrosion can be aggravated by water

Polymers: Sediments that can plug fuel filters and coat

metal surfaces

Class I & II metals: Ca/Mg/Na/K

Calcium & Magnesium & Sodium & Potassium can be in biodiesel as abrasive solids or soluble metallic soaps.

Solids contribute to injector, fuel pump, piston, and ring wear, & engine deposits.

Soluble metallic soaps have little effect on wear, but filter clogging & engine deposits

These compounds may also be collected in exhaust particulate removal devices

Less Critical Parameters Cetane Distillation Temperature Viscosity Carbon Residue Phosphorus Copper Strip Corrosion

Fleet and Distributor Biodiesel Testing

Saftest Completeness of Reaction (3/27 Methanol Test) Soap test: AOCS method Wilkes Infraspec Paradigm Sensors Fleet Biodiesel pHLip Test Wika Water test Microbial growth, algae-x

MP Biomedicals

Completion of Reaction Dissolve 3 ml of biodiesel in 27 ml of

methanol. The biodiesel should be fully soluble in

the methanol forming a clear bright phase.

If you observe un-dissolved material at the bottom of the sample the reaction did not proceed to completion

Each ml of undissolved material corresponds to 4% by volume.

0.2139 Bound GlycerinAlthough cloudy, there were no droplets of precipitate.

0.0900 Bound GlycerinCrystal clear, no cloudiness or precipitate.

Samples Passing 3/27

0.9256 Bound GlycerinNote the falling droplets of unreacted oil.

Samples Failing 3/27

1.8260 Bound Glycerin

Biodiesel Conversion Test

Acid Number Qualitative Tests

Soap- AOCS test method Gels at ambient temperature as little as 5% Cause problems with glycerol separation and

washing Soap can be split by acidulating Soap is usually clear and very viscous Methanol will act as a cosolvent and keep soap in

solution with the biodiesel High soap levels = high sulfated ash number High FFA and water content lead to soap formation

in process

Soap TestTitrating from blue/green to straw yellow….

Wilkes InfraSpecmeasures percent biodiesel in diesel fuel, ethanol in gasoline, water in ethanol as well as total glycerides during the biodiesel

pass/fail determination in less than 5 minutes.

Paradigm Sensors

* Paradigm Sensors’i-SPEC™ tests TOTAL GLYCERIN in blended fuels (B6-B20), which is in accordance with ASTM proposal that the biodiesel portion of the fuel must meet ASTM 6751 prior to blending.

Fleet Biodiesel

pHLip Test

Wika Water Test

Microbial growth Certain varieties of bacteria and fungi can grow in diesel fuel

tanks. Growth occurs at the interface of the fuel and water at the

bottom of the fuel tank. Water must be drained from tank bottoms on a regular basis. ULSD Biocides are available to control microbial growth.

Dead microbes can still plug filters. Water elimination and prevention is preferred over treatment.

Bacteria Growth

Fungal Growth

Operational issues Microbial growth – ULSD & moisture Treat your storage tanks for moisture/biocide Incomplete reaction Aged fuel Cold Flow Low energy content (not harmful)

Fuel filter plugging is the most common

operational issue

Certificate of Analysis

Biodiesel Quality Standard

ASTM D 6751 Standards Fuel quality is critical

for proper functioning Standards ensure

satisfactory operation in diesel engines

BQ 9000 Certification Certifies biodiesel

producers and markers Feeling of confidence for:

Biodiesel Producers Engine and Vehicle

Manufacturers Distributors Consumers

In Summary

Purchase fuel from known quality producer

On-site and in-process analysis is essential

Watch for residual contamination Correct product handling and storage

procedures is essential Final product must meet the current

revision of ASTM D 6751

Biodiesel Fuel Quality Resources www.biodiesel.org http://www.bq-9000.org/ www.me.iastate.edu/biodiesel http://www.uidaho.edu/bioenergy/index.html http://www.cytoculture.com/ http://www.biodieselmagazine.com

NBB Resources

•www.biodiesel.org• Technical Library• Biodiesel Bulletin• Educational Videos Available• Informational Resources• Technical Resources• On-line Database & Spec Sheets

•www.BQ-9000.org • Biodiesel Quality Certification Program for Accredited Producers and Certified Marketers